(Reuters) – Wall Street giant Morgan Stanley’s global co-head of institutional equities David Russell would be retiring after 32 years with the investment banking powerhouse, according to an internal memo seen by Reuters on Monday. Following the retirement, effective at the end of the year, Alan Thomas and Gokul Laroia will continue as global co-heads of the unit. Laroia will also continue to serve in his current role of chief executive of Morgan Stanley Asia Pacific, the memo added. Trading has been a bright spot for the bank this year amid a slump in core revenues from investment banking in …